The following abbreviations are herewith defined, at least some of which are referred to within the following description.                3GPP: Third Generation Partnership Project        ACK: Positive Acknowledgement        ARQ: Automatic Repeat Request        C-DAI: Cell-Domain Downlink Assignment Indicator        C-TAI: Cell-Domain Total Assignment Indicator        CA: Carrier Aggregation        CB: Codebook        CBS: Codebook Size        CC: Component Carriers        CG: Cell Group        DCI: Downlink Control Information        DL: Downlink        eNB: Evolved Node B        FDD: Frequency-Division Duplex        HARQ: Hybrid Automatic Repeat Request        HARQ-ACK: Hybrid Automatic Repeat Request Acknowledgment        LSB: Least Significant Bit        LTE: Long Term Evolution        MCS: Modulation and Coding Scheme        MSB: Most Significant Bit        NAK: Negative Acknowledgement        OFDM: Orthogonal Frequency Division Multiplexing        PCell: Primary Cell        PDCCH: Physical Downlink Control Channel        PDSCH: Physical Downlink Shared Channel        PUCCH: Physical Uplink Control Channel        PUSCH: Physical Uplink Shared Channel        RRC: Radio Resource Control        SC-FDMA: Single Carrier Frequency-Division Multiple Access        SCell: Secondary Cell        TB: Transport Block        TDD: Time-Division Duplex        UE: User Entity/Equipment (Mobile Terminal)        UL: Uplink        UL/DL: Uplink/Downlink        WiMAX: Worldwide Interoperability for Microwave Access        
In wireless communication networks, for example, in LTE systems, error-control feedback is generated in response to received downlink (DL) transport blocks (TBs). This feedback supports error-control procedures, such as hybrid ARQ (HARQ), in the downlink. A user equipment (UE) configured with multiple serving cells in the DL, generates error-control feedback for each of the multiple serving cells. In certain wireless communication networks, such as those conforming to 3GPP LTE Release 8 and onwards, the DL TBs are carried on a Physical Downlink Shared Channel (PDSCH). Depending on configuration, an LTE system transmits a maximum of two TBs on the PDSCH in one serving cell and in a single subframe. HARQ acknowledgement (HARQ-ACK), as used herein, represents collectively the Positive Acknowledge (ACK) and the Negative Acknowledge (NAK) feedback to a received TB. ACK means a TB is correctly received, while NAK means a TB is erroneously received.
Many wireless communication networks also support carrier aggregation (CA). For example, LTE systems conforming to 3GPP LTE Release 10 and later support this feature. In CA, a plurality of component carriers (CC) are aggregated at the UE in order to increase the bandwidth, and thus improve data rate. At most 5 serving cells can be aggregated in the DL in LTE systems conforming to 3GPP LTE Releases 10-12. The number and set of aggregated serving cells is configured by higher layer signaling, for example via radio resource control (RRC) layer signaling. Within one subframe, a UE can receive TBs on multiple serving cells, which increases the UE's data rate.
The HARQ-ACK feedback bits corresponding to the PDSCH are transmitted either on the Physical Uplink Control Channel (PUCCH) or on the Physical Uplink Shared Channel (PUSCH). For a frequency-division duplex (FDD) LTE system, the HARQ-ACK bits corresponding to PDSCH received in subframe n−4 are transmitted in subframe n. For a time-division duplex (TDD) LTE system, the HARQ-ACK bits corresponding to PDSCH received in subframe n−k, where k belongs to the downlink-association set K, is transmitted in subframe n. Note that for LTE-TDD, the elements in set K depends on the TDD uplink/downlink (UL/DL) configuration, as well as the subframe index n. Table 1 depicts exemplary downlink-association sets K, for different combinations of TDD UL/DL configurations and subframes n.
TABLE 1Downlink-association set K: {k0, k1, . . . kM−1} for TDDUL/DLSubframe nConfiguration01234567890——6—4——6—41——7, 64———7, 64—2——8, 7, 4, 6————8, 7, 4, 6——3——7, 6, 116, 55, 4—————4——12, 8, 7, 116, 5, 4, 7——————5——13, 12, 9, 8, 7, 5, 4, 11, 6———————6——775——77—
For a UE configured with multiple serving cells in the DL, when it needs to transmit HARQ-ACK feedback in an UL subframe, the UE needs to determine the HARQ-ACK codebook, i.e., the set of HARQ-ACK feedback bits to be transmitted in the UL subframe. It is important that the eNB and the UE have the same understanding on the HARQ-ACK codebook size as well as the HARQ-ACK feedback bit ordering, such that the HARQ-ACK feedback can be reliably received at the eNB side.
For an LTE-FDD system conforming to 3GPP LTE Releases 10-12, the HARQ-ACK codebook size is determined based on the number of configured serving cells and the transmission mode configured for each serving cell. For an LTE-TDD system conforming to 3GPP LTE Releases 10-12, the HARQ-ACK codebook size is determined based on the number of configured serving cells, the transmission mode configured for each subframe, and the set K associated with the UL subframe n in which the HARQ-ACK shall be transmitted. Multiple transmission modes are defined by 3GPP LTE, where some transmission mode supports transmission of at most one TB in a DL subframe on a serving cell while other transmission mode supports transmission of at most two TBs in a DL subframe on a serving cell. While this solution works for small sets of aggregated serving cells (e.g., five serving cells or less), the current solution becomes unwieldy for larger sets of aggregated serving cells (e.g., 32 serving cells or more).
Further, when HARQ-ACK is transmitted on PUCCH, the PUCCH transmission power for HARQ-ACK is determined based on the number of information bearing HARQ-ACK feedback, instead of the HARQ-ACK codebook size determined based on the number of configured serving cells.